The invention pertains to resonant sensors, and particularly to resonant integrated microbeam sensors (RIMS). More particularly, the invention pertains to integrated transistor and RIMS oscillators.
A single transistor-resonant microbeam device was developed for narrow-band filter applications in the 1960's, and was called the "resonant gate transistor", or "RGT". In the case of the RGT, an integrated oscillator (self-resonance) was demonstrated, but it required the use of two RGT devices tuned to the same frequency. Both devices revealed a 90 degree phase shift at resonance, and the additional 180 degree phase shift was obtained by applying the signal to the beam of one, rather than on the drive electrode. The analysis of the resonant gate transistor is basically applicable to the invention, and shows that even if the actual voltage gain of the transistor-resonant microbeam pair is less than unity, the overall open loop gain can be greater than unity, because the electrostatic drive and capacitive sensing of the vibrating element essentially amplifies the input voltage by a factor of Q at the resonant frequency.